Such a platform has legs which, at the end of the operation must engage predetermined parts of the support structure. These parts are usually piles projecting above the surface of the water, and the legs are generally made fast thereto by welding.
In waters that are protected from swell, such an operation is performed relatively easily by simply ballasting the barge.
At sea, one of the major difficulties arises from the fact that swell applies a horizontal back-and-forth motion to any floating body relative to the sea bed, in addition to the more obvious up-and-down motion. However, to connect the platform to its support structure it is necessary for all the corresponding legs and piles to be in coincidence.
Swell is not entirely uniform, and generally comprises series of waves interspersed with periods of relative calm. It is thus essential to be able to fix the horizontal position and orientation of the platform during the time allowed by such periods of relative calm. In most seas such periods last for less than one minute.
One conventional solution is to suspend the platform from a barge-mounted crane, and to let it drop suddenly at a moment when the legs and the piles coincide. Crane operators are capable of reacting quickly enough to perform such a manoeuver.
This type of solution requires exceedingly heavy equipment for platforms that weigh more than about one thousand tons.
The aim of the present invention is to provide a cheaper system capabale of providing quasi-instantaneous connection between the legs of a platform and the tops of piles intended to receive said legs.